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Question: Answered & Verified by Expert
If the conjugate of $(x+i y)(1-2 i)$ is $(1+i)$, then
MathematicsComplex NumberTS EAMCETTS EAMCET 2017
Options:
  • A $x+i y=1-i$
  • B $x+i y=\frac{1-i}{1-2 i}$
  • C $x-i y=\frac{1-i}{1+2 i}$
  • D $x-i y=\frac{1-i}{1+i}$
Solution:
2525 Upvotes Verified Answer
The correct answer is: $x+i y=\frac{1-i}{1-2 i}$
We have,
Conjugate of $(x+i y)(1-2 i)$ is $1+i$.
i.e. $\quad(x-i y)(1+2 i)=1+i$
$\Rightarrow \quad x-i y=\frac{1+i}{1+2 i}$
Taking conjugate both sides, we get
$$
x+i y=\frac{1-i}{1-2 i}
$$

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